Presently, sodium hyaluronate, a naturally occurring material, is used as a replacement fluid for eyes and joints.
Water soluble polyurethane polymers having varying amounts of water have been known for use as microcapsules for drug delivery, culture media, cosmetics and the like.
U.S. Pat. No. 5,000,955--Gould et al., of common ownership and partial common inventorship herewith--discloses thermally reversible hydrogels made from polyurethane polymers, comprising water and a gel forming hydrophilic polyurethane polymer, made by adding an alkylene diisocyanate with a glycol component comprising polyoxyethylene glycols in a mole weight ratio of NCO/OH from 0.9/1 to about 0.98/1. The reaction mixture is anhydrous. To obtain dry materials, the reactants are subjected to heat, vacuum or a desiccating agent. The glycols are dried since they often contain sufficient water which may alter the properties of the gel.
U.S. Pat. No. 4,810,582--Gould et al., of common ownership and partial common inventorship herewith--discloses NCO/OH ratios of 0.5/1 to 0.9/1 and water levels of 0.1% to 0.5% for use in water insoluble hydrophilic polyurethane polymers.
U.S. Pat. No. 4,810,582 teaches the use of hydrophilic polyurethane hydrogels to encapsulate active agents, wherein the active agent is leached from the water swellable, water insoluble and water soluble polyurethane polymers. The hydrogels are useful as nontoxic culture media, gel matrices, and bacterial cells, and function as nontoxic media for electrophoretic separation of biological substances. The hydrogels are useful in cosmetic applications, as in the preparation of face masks, for example.